This application claims the priority of Japanese Patent Application No. 2002-79167 filed on Mar. 20, 2002, which application is incorporated herein by reference.
1. Technical Field
The present invention relates to a polarized lens of plastic lamination and the production method thereof, in more details, pertaining to such polarized plastic lens as being highly consistent in quality and excellent in durability in comparison with the prior counterparts and the method for producing the same lens in an efficient and economical manner.
2. Prior Art
Conventionally, the following three methods of producing a polarized plastic lens that is used for shading the sunlight or protecting the eyes of the operators working in harsh environments and conditions are known.
(1) A blanking and hot machining method wherein a polarized film made from poly (vinyl alcohol) whose surfaces are coated with an adhesive is interposed for pasting between two synthetic resin thin plates, and the plastic polarized article as obtained is subjected to blanking operation so as to be formed into a circular shape, which article is subjected to vacuum forming operation within an electric furnace so as to produce a polarized lens with curvature.
(2) An injection mold-heat bonding method wherein a synthetic resin, from which resin a lens matrix layer is molded, is injected into a metallic mold and a polarized plate made from polycarbonate resin is press-bonded onto the convex surface of the matrix layer while the synthetic resin as injected is still sticky under heat so as to produce a polarized lens.
(3) A sandwiching method wherein a polarized film made from poly (vinyl alcohol) whose surfaces are coated with an adhesive is sandwiched between two plastic lens plates with curvature so as to produce a polarized lens. To note, hard-coating treatment by such conventional method as dip coating is performed on the surfaces of the polarized lens as produced by the above three methods.
However, as to the above blanking and hot machining method, the circular polarized plastic article is subjected to high-temperature molding heat during the vacuum forming operation so as to tend to bring the quality of the finished products into inconsistency, in addition to which the curvature of the lens as formed by the vacuum forming operation chronologically fails and there arises distortion on the surface thereof as well as the polarized lens as obtained is easily subjected to aberration owing to residual stress.
As to the above injection mold-heat bonding method, the synthetic resin polarized plate does not just fit the surface of the matrix layer so as to allow air bubbles to occur at the interface thereof while as to the above sandwiching method, it allows air bubbles to occur at the interface between the polarized film and the respective plastic lens plates so as to make the hue of the polarized lens as obtained inconsistent. Any of the conventional polarized lenses as mentioned above lacks uniformity in quality and is poor at yielding, which results in the increase of the number of defects as well as the production cost. Thus, a plastic polarized lens of higher quality and reasonable price is hoped for.
In view of the above inconveniences encountered with the conventional plastic polarized lens as adopted for sunglasses and eyes-protection glasses, the present invention is firstly to provide a plastic polarized lens that is highly consistent in quality and excellent in durability in comparison with such prior polarized lens as produced by the above methods (1), (2) and (3).
Further, the present invention is secondly to provide a method for efficiently producing a high-quality plastic polarized lens wherein the adoption of a casting resin essentially consisting of diethylene glycol bis(allyl carbonate) having lower viscosity and higher ductility prevents distortion or air bubbles from occurring at the interfaces between the respective plastic laminations.
Further, the present invention is thirdly to provide a method for economically producing a high-quality plastic polarized lens free from such quality problems as aberration by restraining the occurrence of defects almost to none.
The means to solve the above issues is described below with reference to the accompanying drawings.
The first issue of the present invention is solved by laminating the concave side surface of the polarized film layer 1 made from poly (vinyl alcohol) resin onto the convex side surface of the lens matrix layer 2 made from polycarbonate resin through the polymerization setting layer 3 made from diethylene glycol bis(allyl carbonate) resin and forming the polymerization setting layer 4 made from ethylene glycol bis(allyl carbonate) resin on the convex side surface of the polarized film layer 1 so as to provide the plastic polarized lens of an integrally laminated structure comprising the respective layers 1, 2, 3 and 4.
The second and third issues of the present invention are solved by adopting a method comprising the steps of dropping a casting resin R of lower viscosity essentially consisting of ethylene glycol bis(allyl carbonate) into a concave cavity C of a casting die D; overlaying a convex side surface of a polarized film 1xe2x80x2 made from poly(vinyl alcohol) resin, which side surface corresponds to the concave surface of the cavity C, onto the cavity C so as to uniformly spread and attach the casting resin R onto the convex side surface of the polarized film 1xe2x80x2; dropping the casting resin R into the concave side surface of the polarized film 1xe2x80x2 and overlaying a convex side surface of a lens matrix plate 2xe2x80x2 made from polycarbonate resin onto said concave side surface of said polarized film 1xe2x80x2 with said casting resin R thereon so as to uniformly spread and attach the casting resin R onto the convex side surface of the lens matrix plate 2xe2x80x2; polymerizing and setting the casting resin R as uniformly spread and attached on said convex side surfaces of said polarized film 1xe2x80x2 and said lens matrix plate 2xe2x80x2 under heat treatment so as to obtain an integral polarized lens prototype Lb; and performing finishing operation on said prototype Lb so as to produce a polarized lens L of plastic lamination.